1 . Priority Claim
This application claims the benefit of priority from German Patent Application No. DE 10 2005 014 176.5, filed Mar. 29, 2005, which is incorporated by reference herein.
2. Technical Field
The disclosure generally relates to a method for producing a protective assembly for protecting an electronic component from electrostatic discharge (ESD), in particular to allowing non-diverted electrostatic discharge to propagate between various portions of the circuit, the propagation of high-frequency interference at the same time being prevented.
3. Related Art
There is a need to protect integrated circuits from electrostatic discharge (ESD) caused, for example, by contact with a person. A circuit may be provided, for example, with protective elements at bond pads of the circuit, which are circuit input or output terminals The protective elements divert an electrostatic discharge to a circuit supply potential, such as a positive supply voltage, a negative supply voltage, or a ground line. Protective elements of this type are described, for example, from US 6,433,985 B1, the whole content of which is incorporated by reference for all purposes.
In addition, a remaining portion of the electrostatic discharge, i.e. a portion that was not diverted to the outside by the protective elements and via the supply potential, is allowed to propagate via a supply voltage system of the integrated circuit. In the event of an electrostatic discharge, any voltage drop in or on the integrated circuit must be kept as low as possible in order to be able to ensure effective protection of susceptible circuit parts. In addition, the path for propagation via the supply voltage system should be configured in such a way that, during normal operation of the circuit, interference signals generated in a portion of the integrated circuit are not able to propagate in an arbitrary fashion via this propagation path. Propagation between a digital part of the circuit and an interference-susceptible analog part of the circuit should, for example, be prevented.
For this purpose, it may be possible to connect two antiparallel diodes between a supply voltage line of a first circuit portion and a supply voltage line of a second circuit portion. These diodes are configured in such a way that, even in the forward direction, a specific voltage must be applied for them to become conductive.
If, for example, a portion of electrostatic discharge is then applied to the supply voltage line of the first circuit portion, the voltage thereby produced is sufficient for a correspondingly polarized diode of the antiparallel diodes to become conductive, thus enabling the electrostatic discharge to propagate to the supply voltage line of the second circuit portion. High-frequency interference, on the other hand, which conventionally has substantially lower voltages than electrostatic discharge, is not able to propagate via the antiparallel diodes. The first circuit portion may therefore be isolated from the second circuit portion with respect to high-frequency interference.
A drawback of this configuration may be that in the event of electrostatic discharge, there may be a relatively high voltage drop across the antiparallel diodes, leading to a corresponding increase in voltage at the parts to be protected in the circuit. Configurations of this type may therefore not be used in what are known as low-voltage technologies, since maximum tolerable voltages at the circuit portions may be exceeded.
It has been proposed, in this regard, to provide within the integrated circuit a connection, having a specific minimum inductance, between the supply voltage line of the first circuit portion and the supply voltage line of the second circuit portion. Isolation may be achieved in the case of high-frequency interference signals, while electrostatic discharge is able to propagate almost unimpeded. However, a solution of this type disadvantageously takes up chip surface area, and this increases the production costs. Moreover, a solution of this type may not be used in electronic components in which two chips are integrated in a single component.
Therefore a need exists for producing a protective assembly for protecting an electronic component from electrostatic discharge, wherein electrostatic discharge is able to propagate via a supply voltage system of circuit portions contained in the electronic component, while the propagation of high-frequency interference is prevented. It should be possible to carry out the method cost-effectively and, in particular, to use the method for what are known as laminate packages such as, for example, ball grid arrays (BGAs), in which external terminals consist of “solder balls” conventionally attached to the lower side of the packaging of the electronic component.